How Do Doctors Test for Ebola?

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Health officials are now monitoring 50 people in Texas for signs
of Ebola, via twice-daily temperature checks, and in recent days,
there have been reports that people in other areas of the country
— most recently, Washington, D.C. — may be infected with the
virus.

But why can't all these people just be tested for Ebola as soon
as possible?

Ebola
is difficult to diagnose when a person is first infected because
the early symptoms, such as fever, are also symptoms of other
diseases, such as malaria and typhoid fever.

"The symptoms are extremely nonspecific in the beginning — Ebola
looks like almost anything," said Dr. Bruce Hirsch, an
infectious-disease specialist at North Shore University Hospital
in Manhasset, New York. [ Ebola
Virus: 5 Things You Should Know ]

Who could have it?

The main question doctors consider is whether the person has been
in one of the countries in West Africa experiencing the current
Ebola outbreak (Guinea, Sierra Leone or Liberia) within the
last 21 days, which is the incubation period of the virus, Hirsch
told Live Science. Or, whether that person has been exposed to
someone has been one of those places, he added.

Earlier this week, a man in Texas became the first person to be
diagnosed with Ebola in the United States, after traveling to
Dallas from Liberia. The patient sought medical care but was
initially sent home, before being admitted to a hospital in
Dallas and testing positive for the virus.

Ebola spreads via contact with the blood or bodily fluids of an
infected person, objects contaminated with those fluids or
contact with infected animals; it does
not spread through the air. Symptoms of the disease include a
fever greater than101.5 degrees Fahrenheit (38.6 degrees
Celsius), severe headache, muscle pain, diarrhea, vomiting,
abdominal pain or unexplained hemorrhage, according to the
Centers for Disease Control and Prevention (CDC).

If a person shows these symptoms and has been in an area with
Ebola within the past 21 days, they should be put in isolation
and tested for Ebola, the CDC says.

Tests for Ebola

A number of tests can be used to diagnose Ebola within a few days
of the onset of symptoms, which can detect the virus's genetic
material or the presence of antibodies against the pathogen.

The most accurate of these is likely the polymerase chain
reaction (PCR) test, a technique that looks for genetic material
from the virus and creates enough copies of it that it can be
detected, Hirsch said. "PCR is a really definitive test," Hirsch
said. It can pick up very small amounts of the virus.

However, this test can be negative during the first three days an
infected person has symptoms, said Dr. Sandro Cinti, an
infectious-disease specialist at the University of Michigan
Hospital System/Ann Arbor VA Health System.

"Somebody could be in the hospital for three to five days before
a diagnosis [of Ebola] is confirmed," Cinti told Live Science.
"The important thing is keeping the patient isolated until you
can get to a diagnosis." Meanwhile, doctors will be running tests
to rule out other diseases, such as malaria, which can be
detected more quickly than Ebola, he said.

Another test for Ebola looks for antibodies produced by the
body's immune system in response to the virus. Known as the
antigen-capture enzyme-linked immunosorbent assay (ELISA), this
test can take even longer than three days to give a positive
result for an infected person, Cinti said. And antibodies can
also be detected after a patient recovers, he added.

Once a patient is diagnosed with Ebola, scientists may attempt to
isolate
the virus — which is a type of filovirus, known for their
filamentlike shape — by culturing it with living cells and
examine it using electron microscopy. But culturing Ebola is very
dangerous, and should only be done in a high-biosafety-level lab,
Hirsch said. Culturing the virus is not a practical means of
diagnosing infection, but may help researchers understand how the
virus infects cells and test possible treatments.

So, given the severity of an Ebola infection, why wouldn't you
test everybody with the remotest chance of having the disease?

A huge number of people come to the United States from Africa
with fevers, Cinti said, and testing all of them for Ebola would
drain hospital resources and raise unnecessary panic. "We really
have to be clear and get good histories about exposure," he said.
"It makes absolutely zero sense to test people who aren't from
high-risk areas."